<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>颜色-透明</title>
    <style>
        body{
            margin: 0;
            padding: 0;
            font-family: 微软雅黑;
            background-color: #f7f7f7;
        }
        ul{
            margin: 0;
            padding: 0;
            list-style: none;
        }
        .wrapper{
            width: 1024px;
            margin: 0 auto;
        }
        .wrapper > section{
            min-height: 300px;
            margin-bottom: 30px;
            box-shadow: 1px 1px 4px #DDD;
            background-color: #fff;
        }
        .wrapper > header{
            text-align: center;
            line-height: 1;
            padding: 20px;
            margin-bottom: 10px;
            font-size: 30px;
        }
        .wrapper section > header{
            line-height: 1;
            padding: 10px;
            font-size: 22px;
            color: #333;
            background-color: #EEE;
        }
        .wrapper .wrap-box{
            padding: 20px;
        }

        /* 颜色的表达方式 red、 rgb() #FFF */
        /* 透明度 opacity  transparent */
        .parent{
            width: 200px;
            height: 200px;
            background: red;
        }

        .child {
            width: 100px;
            height: 100px;
            background: transparent;
        }
    </style>
</head>
<body>
    <div class="wrapper">
        <header>CSS3-透明度</header>
        <section>
            <header>opacity</header>
            <div class="wrap-box">
                <p>子元素会继承父元素的透明度</p>
            </div>
        </section>
        <section>
            <header>transparent</header>
            <div class="wrap-box">
                <p>完全透明，类似玻璃一样</p>
                <div class="parent">
                    <div class="child"></div>
                </div>

            </div>
        </section>

    </div>
</body>
</html>